[Image-SIG] Reading a 8bit Tif image from ArcMAP doesnt read well

German Ocampo gerocampo at gmail.com
Thu Oct 28 18:56:13 CEST 2010


Many thanks for your email.I want to read values from images in
grayscale or rgb, because the product that is coming from Arcmap could
be either.

The issue is that using PIL I get pixel values in the greyscale of 127
or rgb(0,0,0), where really I could see in Gimp that these pixels have
a different value. Looks like PIL can decode part of the picture and
another part of the picture not.

Also I tried today to read the pixel values of the picture using
temp=np.array(im) but still I got  some cells with a value of 127
where really the image has different values.

The only way to decode the picture was using freeImagepy, opening the
image with freeImagepy, saving and then open again with PIL to get the
values. It works but not in the way that supose to be. I want to do
all with PIL :-)
 (Attached is the code)

Many thanks


    from PIL import Image
    from PIL import TiffImagePlugin
    import numpy as np
    import sys
    import FreeImagePy
    FIPY = FreeImagePy.freeimage()
    image = FIPY.genericLoader(file_tif)
    FIPY.Save(FreeImagePy.FIF_TIFF, image, "temp.tif")

   im = Image.open("temp.tif")
   for i in range(0,size_y):
       for j in range(0,size_x):
           if mode=="RGB":
               print cont,temp[cont]
               if color in list_colors:

On Thu, Oct 28, 2010 at 4:26 PM, Chris Mitchell <chris.mit7 at gmail.com> wrote:
> Why would the image go between greyscale and rgb?  In anycase, perhaps
> the easiest solution is use np.resize on temp instead of the for
> loops.  Then if you have tuples of rgb versus ints you can use
> np.where()
> On Thu, Oct 28, 2010 at 4:36 AM, German Ocampo <gerocampo at gmail.com> wrote:
>> Good morning
>> Im reading an 8bit image generated by ArcMap using PIL in windows, the
>> image load well without error messages but, when I try to extract the
>> values to a numpy array I got some lines of the image with value of
>> pixel 127 (greyscale) or rgb(0,0,0). When I open the image using GIMP
>> or arcmap  I could see that the image is complete.
>> Any idea of what is happening??
>> the code that I'm using for read the image is:
>>     from PIL import Image
>>     from PIL import TiffImagePlugin
>>    import numpy as np
>>    import sys
>>    im = Image.open(file_tif)
>>    values=np.zeros((size_y,size_x))
>>    mode=im.mode
>>    temp=list(im.getdata())
>>    cont=-1
>>    list_colors=[]
>>    for i in range(0,size_y):
>>        for j in range(0,size_x):
>>            cont+=1
>>            if mode=="RGB":
>>                color=temp[cont]
>>                print cont,temp[cont]
>>                if color in list_colors:
>>                    index=list_colors.index(color)
>>                    values[i][j]=index+1
>>                else:
>>                    list_colors.append(color)
>>                    values[i][j]=len(list_colors)
>>            else:
>>                values[i][j]=temp[cont]
>> Best regards
>> German
>> _______________________________________________
>> Image-SIG maillist  -  Image-SIG at python.org
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